Yes, there's an option to enable blocking. I think it should be the other way around, which was kind of my whole point. That's the only way to encourage site owners to stop designing sites that break when they can't spy on users.
As things stand, it's a hard sell to have a browser do something that breaks sites that used to work. Most users tend to not be happy about it. This is definitely an area worth pushing on; the question is how best to do it.